1. Field
The present invention relates generally to computer graphics and, more specifically, to stylistic renderings of three-dimensional (3D) models.
2. Description
Engraving is a traditional graphical technique used in various arts. If an artist wants to create a print from a copperplate engraving, the conventional method is to use a graver's tip to carve out a copperplate by making furrows in it. The furrows are filled with ink. The plate is then pressed onto paper or another medium to create the artwork. This is a time consuming process and any mistakes that are made during engraving are costly, because fixing errors may require the artist to start the engraving over with a new copperplate. FIG. 1 shows two examples of traditional copperplate engravings.
Modern computer graphics may be used to transform traditional engraving into a digital art through non-photo-realistic rendering (NPR) techniques. Unlike photo-realistic rendering techniques, the goal of NPR is to create an aesthetic experience that is deliberately unrealistic in such a way that the artist conveys to the user a feeling of personal style, sketchiness, incompleteness, fiction, or emotion. As examples, computer rendered charcoal prints can express the style of the artist; architectural blueprints are often rendered as sketchy to imply that they are simply a draft, and cartoon characters are rendered in such a manner as to convey fiction and humor. Various existing artistic styles may be adapted to NPR and used as stylistic rendering methods for computer-generated artwork. Digital engraving is one such technique being developed for content creation activities for original artwork, web pages, animated films and cartoons, computer games, and other applications.
One implementation of digital engraving that imitates traditional copperplate engraving for portraits is described in “Digital Facial Engraving”, by Victor Ostromoukhov, of the Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland, Proceedings of SIGGRAPH 1999, Los Angeles, Calif. Ostromoukhov's technique creates non-real-time digital engraving of two-dimensional (2D) images using a computer. This technique appears to work reasonably well for 2D images. Ostromoukhov's user-driven method of placing texture patches are true to form and in the spirit of facial engraving. However, there are at least several drawbacks to this method. Ostromoukhov's method requires user intervention to author an engraved image (e.g., it's a manual process), operates only on a single view in two dimensions, and cannot be performed in real-time.
Further advances in digital engraving techniques that overcome these and other disadvantages of the prior art would be valuable to digital content creators.